This invention relates to a pressure relief device for an engine room of a small watercraft which prevents the pressure in the engine room from exceeding a predetermined level of pressure by relieving the pressure inside.
The engine room, defined by an engine encasement, for small watercrafts is sealed with a cover on the opening of the engine encasement because small watercrafts, especially for sports, are apt to overturn at sea and take on water.
Since engine room space for such small watercrafts is relatively limited, if the engine encasement is hermetically sealed, the inside pressure will increase in case that a high temperature and high pressure exhaust gas leaks at engine-exhaust tube joints or the exhaust silencer fittings from vibrations produced by the engine, propeller and hull while sailing. If the engine cover is loosely fastened to the joints on the upper hull to relieve the increasing pressure, and the hull happens to be subjected to impacts due to the waves against the watercraft under sail, the shocks may cause the joints to work out of place, thus leading to the engine cover being flung away, or cause the watertightness between the engine cover and the upper hull to be poor, thus allowing the water to enter the engine room and rust the engine, resulting in troubles.
On the contrary, if said joints are tightly fastened to cope with the above mentioned troubles, this may generate such a high pressure in the engine room that the engine cover would be explosively removed by shocks from the waves or the like.